Nicholas (Nick) King, 14, was shot in the neck last Tuesday, when a 15-year-old friend pointed a loaded rifle at him and pulled the trigger.
The male teen who pulled the trigger told police he did not know the gun was loaded. King was fatally wounded by the shot.
Police were called to the scene just after 8 p.m. local time. King was pronounced dead within minutes of their arrival.
The slain teen's mother, Lori King, was working at a variety store when she got the call about her son's death.
King said she initially thought it was a prank, given that it was the night before Halloween.
"I just thought it was a joke," she told CBC News in a telephone interview from Indianapolis.
But it wasn't. She soon spoke to police and a chaplain.
King said she had to call Nick's father, and later her own parents, to tell them what happened.
"I shouldn't have to call my mom and dad … and say that Nick is dead," she said.
Nick King was born in Oshawa, Ont., but moved to the United States when he was a child.
"Canada has always been home to Nick," his mother said.
A memorial service was held in Indianapolis on Saturday. Nick will be buried in Oshawa, Ont., next weekend.